Head injuries and various diseases have been known to cause increases in intracranial pressure, which can pose a danger to the patient. Large uncontrolled increases in intracranial pressure may result in brain injury or impairment, permanent or temporary, of neuromotor functions. Thus, in some patients, it is desirable to monitor the intracranial pressure, and to provide a means for draining excess cerebrospinal fluid from the cranial vault to control the pressure when such drainage is indicated.
Because pressure monitoring and drainage procedures are invasive, some degree of trauma to the patient occurs. It is desirable to keep such trauma to a minimum while still allowing the invasive instrument to perform its function. In the case of drainage, a relatively large lumen or set of lumina are desired so that the fluid can be drained at a relatively fast rate and the pressure can be brought rapidly under control. However, the size of the catheter containing such lumina must be limited so that trauma to the patient is not excessive. In many cases, it is preferable to also insert a pressure sensor into the cranial cavity to directly measure intracranial pressure for increased accuracy. Pressure sensors typically involve multiple parts and may likewise be of substantial size, although it is desirable to limit their size also to reduce trauma to the patient.
Typically, intracranial pressure monitoring catheters and ventricular drainage catheters have been insertable into the patient through a burr hole formed in the skull. In some instances, the catheters have been designed for insertion through a subcutaneous tunnel which extends beneath the patient's scalp, adjacent the skull burr hole through which the catheter is inserted. It is believed that such scalp tunnel insertion techniques decrease the risk of intracranial infection. Providing an elongate tunnel through which pathogenic organisms would have to pass prior to passing through the skull burr hole and into the cranium makes it much more difficult for such organisms to enter the cranium.
During the treatment of a patient where control of the cranial pressure is necessary through drainage of the cerebrospinal fluid, it is desirable to monitor the pressure while the fluid is being drained so that excessive drainage does not occur. However, placing two separate catheters in the cranium, one containing a pressure sensor and the other containing a drainage lumen, is undesirable due to the trauma to the patient that would result and the increased chances for infection. In some cases, treatment for severe head injuries or diseases can take many days if not longer and exposing the cranium to the possibility of infection through the insertion of two separate catheters may be clinically unacceptable.
Another consideration in the construction of a ventricular catheter is the method of insertion of the catheter distal end into the proper location in the cranium. In some cases, a lumen exists in the catheter for receipt of a stylet. The entry burr hole is made in the skull of the patient, the insertion stylet is inserted into the closed lumen of the distal end of the catheter, and is used to force the catheter through the entry burr hole of the patient and into position. The stylet is then withdrawn and pressure monitoring and drainage procedures begun as necessary. In such a catheter, the stylet must be stiff enough to force the catheter into operational position in the cranium and therefore must have a certain minimum thickness. Additionally, the stylet-receiving lumen in the catheter body must be large enough to accept the stylet, yet strong enough so that the stylet will not puncture the catheter distal tip when introducing the catheter into the patient's skull with the stylet. Because the pressure sensor also has a finite size, and the outer size of the catheter is limited, typically the drainage lumen is smaller than is desirable. This can adversely affect the drainage rate.
In some prior art devices, a ventricular drainage catheter would typically be inserted into the patient. If pressure monitoring were needed, a pressure monitoring catheter would be inserted through the drainage lumen in the drainage catheter, thereby lowering the drainage capability of the drainage catheter.
An example of a catheter that overcomes some of the above deficiencies is shown in U.S. Pat. No. 5,312,357 to Buijs et al. This catheter includes a lumen that may receive a pressure sensor device and another lumen for receiving a stylet for insertion of the catheter into the patient and for drainage once the stylet is removed. However, the closure device is shown as a sleeve that is slid over the opening for the stylet. Such a closure technique can be difficult to use due to the need to slide it over a substantial length of tubing.
It is important that the sleeve make a fluid-tight seal over the stylet opening so that drainage is directed to the proximal end of the catheter. A tight-fitting seal, however, will tend to be difficult to slide into place. Also, a less difficult to slide seal may not fit tightly enough to prevent leakage.
Hence those skilled in the art have recognized a need for a combination pressure monitoring and drainage catheter that has a small outer diameter for reduced trauma to the patient while having the ability to monitor pressure, allow drainage of the fluid in the cranium, and accept a stylet for use in placement of the catheter in the correct position in the cranium. In addition, it has also been recognized that using one large lumen for both drainage and receiving the stylet for installation is desirable. Further, those skilled in the art have recognized a need for an easier means to close the opening of a lumen used to receive a stylet. The present invention fulfills these needs and others.